Door knocker



FIG. 1 is a front elevational view of a door knocker showing my new design;

FIG. 2 is a left side elevational view thereof, the right side elevational view being substantially a mirror image of the left side elevational view;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a door knocker, as shown and described. 